Fixes crash in TileSetAtlasSource::get_tiles_to_be_removed_on_change
Fixes crash in TileSetAtlasSource::get_tiles_to_be_removed_on_change

vnen/godot,Faless/godot,Shockblast/godot,firefly2442/godot,BastiaanOlij/godot,josempans/godot,sanikoyes/godot,akien-mga/godot,godotengine/godot,ZuBsPaCe/godot,josempans/godot,Faless/godot,akien-mga/godot,guilhermefelipecgs/godot,pkowal1982/godot,Zylann/godot,sanikoyes/godot,BastiaanOlij/godot,vkbsb/godot,Faless/godot,godotengine/godot,vkbsb/godot,vnen/godot,vnen/godot,josempans/godot,Shockblast/godot,Valentactive/godot,Valentactive/godot,BastiaanOlij/godot,sanikoyes/godot,Zylann/godot,vnen/godot,BastiaanOlij/godot,godotengine/godot,firefly2442/godot,Zylann/godot,ZuBsPaCe/godot,Faless/godot,guilhermefelipecgs/godot,Zylann/godot,BastiaanOlij/godot,Faless/godot,ZuBsPaCe/godot,firefly2442/godot,firefly2442/godot,guilhermefelipecgs/godot,Shockblast/godot,Valentactive/godot,Zylann/godot,Zylann/godot,josempans/godot,Faless/godot,Faless/godot,pkowal1982/godot,Shockblast/godot,godotengine/godot,Valentactive/godot,josempans/godot,akien-mga/godot,vkbsb/godot,ZuBsPaCe/godot,Shockblast/godot,sanikoyes/godot,guilhermefelipecgs/godot,Zylann/godot,Shockblast/godot,pkowal1982/godot,BastiaanOlij/godot,vnen/godot,pkowal1982/godot,BastiaanOlij/godot,vkbsb/godot,godotengine/godot,sanikoyes/godot,guilhermefelipecgs/godot,BastiaanOlij/godot,sanikoyes/godot,josempans/godot,Valentactive/godot,pkowal1982/godot,firefly2442/godot,ZuBsPaCe/godot,vnen/godot,Valentactive/godot,akien-mga/godot,akien-mga/godot,guilhermefelipecgs/godot,vnen/godot,pkowal1982/godot,josempans/godot,ZuBsPaCe/godot,firefly2442/godot,vkbsb/godot,vkbsb/godot,guilhermefelipecgs/godot,akien-mga/godot,firefly2442/godot,Faless/godot,ZuBsPaCe/godot,sanikoyes/godot,Shockblast/godot,firefly2442/godot,Valentactive/godot,guilhermefelipecgs/godot,akien-mga/godot,pkowal1982/godot,josempans/godot,godotengine/godot,akien-mga/godot,vnen/godot,godotengine/godot,sanikoyes/godot,Zylann/godot,vkbsb/godot,godotengine/godot,Valentactive/godot,pkowal1982/godot,Shockblast/godot,vkbsb/godot,ZuBsPaCe/godot